The fuel cell is configured such that an electrolyte membrane is sandwiched between an anode and a cathode. When hydrogen (fuel gas) is in contact with the anode and oxygen (oxidant gas) is in contact with the cathode, an electrochemical reaction occurs between the two electrodes, thereby generating an electromotive force.
In general, the fuel cell system supplies the fuel gas supplied from a high-pressure hydrogen tank to the anode, and at the same time supplies air drawn from outside by a compressor to the cathode. At this time, in order to reduce the amount of fuel gas to be newly supplied, an anode off gas discharged from the anode is circulated by a circulation device. The circulated anode off gas is mixed with a fuel gas newly supplied from outside and then the mixed gas is supplied to the anode.
However, there is a problem in that moisture contained in an anode off gas is condensed into water, which remains in a pipe for circulating the anode off gas, thereby reducing the amount of flowing anode off gas and thus failing to supply a predetermined amount of hydrogen to the fuel cell.
In view of this problem, there has been proposed a fuel cell device having a passage shut-off valve which is positioned higher than the anode off gas inlet between the anode off gas outlet of the fuel cell and the anode off gas inlet of the circulation device (see Japanese Patent Laid-Open No. 2002-231294). According to this device, the flow of hydrogen can be prevented from being blocked by water in a pipe in which an anode off gas is circulated.